Naphthalene derivative, resist bottom layer material, and patterning process

ABSTRACT

A naphthalene derivative having formula (1) is provided wherein An and Art denote a benzene or naphthalene ring, and n is such a natural number as to provide a weight average molecular weight of up to 100,000. A material comprising the naphthalene derivative or a polymer comprising the naphthalene derivative is spin coated to form a resist bottom layer having improved properties. A pattern forming process in which a resist bottom layer formed by spin coating is combined with an inorganic hard mask formed by CVD is available.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2010-202660 filed in Japan on Sep. 10, 2010,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a naphthalene derivative and a method forpreparing the same. It also relates to a resist bottom layer materialfor forming a resist bottom layer useful as an antireflective coating(ARC) in the multilayer resist process used in micropatterning for thefabrication of semiconductor devices or the like, a method for forming aresist bottom layer, and a pattern forming process adapted for thelithography including exposure to KrF excimer laser (248 nm), ArFexcimer laser (193 nm), F₂ laser (157 nm), Kr₂ laser (146 nm), Ar_(2e)laser (126 nm), soft X-ray or EUV (13.5 nm), electron beam, or X-ray,using the resist bottom layer material.

BACKGROUND ART

While a number of recent efforts are being made to achieve a finerpattern rule in the drive for higher integration and operating speeds inLSI devices, the commonly used light exposure lithography is approachingthe essential limit of resolution determined by the light sourcewavelength.

As the light source used in the lithography for resist patternformation, g-line (436 nm) or i-line (365 nm) from a mercury lamp hasbeen widely used. One means believed effective for further reducing thefeature size is to reduce the wavelength of exposure light. For the massproduction process of 64 M-bit DRAM, the exposure light source of i-line(365 nm) was replaced by a KrF excimer laser having a shorter wavelengthof 248 nm. However, for the fabrication of DRAM with a degree ofintegration of 1 G or more requiring a finer patterning technology(processing feature size 0.13 μm or less), a shorter wavelength lightsource is required. In particular, photolithography using ArF excimerlaser light (193 nm) is now under investigation.

On the other hand, it is known in the art that the bilayer resistprocess is advantageous in forming a high-aspect ratio pattern on astepped substrate. In order that a bilayer resist film be developablewith a common alkaline developer, high molecular weight siliconecompounds having hydrophilic groups such as hydroxyl and carboxyl groupsmust be used.

Among silicone base chemically amplified positive resist compositions,recently proposed were those compositions for KrF excimer laser exposurecomprising a base resin in the form of polyhydroxybenzylsilsesquioxane,which is a stable alkali-soluble silicone polymer, in which somephenolic hydroxyl groups are protected with t-BOC groups, in combinationwith an acid generator (see JP-A H06-118651 and SPIE vol. 1925 (1993),p377). For ArF excimer laser exposure, positive resist compositionscomprising as a base a silsesquioxane of the type in whichcyclohexanecarboxylic acid has substituted thereon an acid labile groupwere proposed (see JP-A H10-324748, JP-A H11-302382, and SPIE vol. 3333(1998), p62). For F₂ laser exposure, positive resist compositions basedon a silsesquioxane having hexafluoroisopropanol as a dissolvable groupwere proposed (see JP-A 2002-55456). The above polymer bears in itsbackbone a polysilsesquioxane containing a ladder skeleton producedthrough polycondensation of a trialkoxysilane or trihalosilane.

Silicon-containing (meth)acrylate polymers were proposed as a resistbase polymer having silicon pendants on side chains (see JP-AH09-110938, J. Photopolymer Sci. and Technol., Vol. 9, No. 3 (1996),p435-446).

The lower (or bottom) layer of the bilayer resist process is formed of ahydrocarbon compound which can be etched with oxygen gas, and must havehigh etch resistance since it serves as a mask when the underlyingsubstrate is subsequently etched. For oxygen gas etching, the bottomlayer must be formed solely of a silicon atom-free hydrocarbon. Toimprove the line-width controllability of the upper (or top) layer ofsilicon-containing resist and to minimize the sidewall corrugation andpattern collapse by standing waves, the bottom layer must also have thefunction of an antireflective coating (ARC). Specifically, thereflectance from the resist bottom layer back into the resist top layermust be reduced to or below 1%.

Now, the results of calculation of reflectance at film thickness varyingup to the maximum of 500 nm are shown in FIGS. 2 and 3. Assume that theexposure wavelength is 193 nm, and the resist top layer has an n valueof 1.74 and a k value of 0.02. FIG. 2 shows substrate reflectance whenthe resist bottom layer has a fixed k value of 0.3, the n value variesfrom 1.0 to 2.0 on the ordinate and the film thickness varies from 0 to500 nm on the abscissa. Assuming that the resist bottom layer of thebilayer resist process has a thickness of 300 nm or greater, optimumvalues at which the reflectance is reduced to or below 1% exist in therefractive index (n) range of 1.6 to 1.9 which is approximate to orslightly higher than that of the resist top layer.

FIG. 3 shows substrate reflectance when the resist bottom layer has afixed n value of 1.5 and the k value varies from 0 to 0.8. Assuming thatthe resist bottom layer of the bilayer resist process has a thickness ofat least 300 nm, the reflectance can be reduced to or below 1% as longas the k value is in a range of 0.24 to 0.15. By contrast, theantireflective coating used in the form of a thin film of about 40 nmthick in the single-layer resist process has an optimum k value in therange of 0.4 to 0.5, which differs from the optimum k value of theresist bottom layer used with a thickness of 300 nm or greater in thebilayer resist process. For the resist bottom layer in the bilayerresist process, a film having a lower k value, that is, more transparentis necessary.

As the material for forming a resist bottom layer in 193 nm lithography,copolymers of polyhydroxystyrene with acrylates are under study asdescribed in SPIE Vol. 4345 (2001) p50. Polyhydroxystyrene has a verystrong absorption at 193 nm and its k value is as high as around 0.6 byitself. By copolymerizing it with an acrylate having a k value of almost0, the k value of the copolymer is adjusted to around 0.25.

However, the resistance of the acrylate to substrate etching is weak ascompared with polyhydroxystyrene, and a considerable proportion of theacrylate must be copolymerized in order to reduce the k value. As aresult, the resistance to substrate etching is considerably reduced. Theetch resistance is not only reflected by the etching speed, but alsoevidenced by the development of surface roughness after etching. Throughcopolymerization of acrylate, the surface roughness after etching isincreased to a level of serious concern.

Also proposed was a tri-layer process of stacking a resist top layer ofa silicon-free single-layer resist film, a resist middle layercontaining silicon below the top layer, and a resist bottom layer oforganic film below the middle layer. See J. Vac. Sci. Technol., 16(6),November/December 1979. Since the single-layer resist generally providesbetter resolution than the silicon-bearing resist, the tri-layer processpermits such a high resolution single-layer resist to be used as animaging layer for light exposure. A spin-on-glass (SOG) coating is usedas the resist middle layer. A number of SOG films have been proposed.

In the trilayer process, the optimum optical constants of the bottomlayer for controlling reflection from the substrate are different fromthose in the bilayer process. The purpose of minimizing substratereflection, specifically to a level of 1% or less is the same betweenthe bi- and tri-layer processes. In the bilayer process, only the resistbottom layer is endowed with the antireflective effect. In the tri-layerprocess, either one or both of the resist middle layer and resist bottomlayer may be endowed with the antireflective effect.

U.S. Pat. No. 6,506,497 and U.S. Pat. No. 6,420,088 disclosesilicon-containing layer materials endowed with antireflective effect.In general, a multi-layer antireflective coating has greaterantireflective effect than a single-layer antireflective coating and iscommercially widely used as an antireflective film for optical articles.A higher antireflective effect is obtainable by imparting anantireflective effect to both a resist middle layer and a resist bottomlayer. If the silicon-containing resist middle layer in the trilayerprocess is endowed with the function of ARC, the resist bottom layerneed not necessarily possess the maximum function of ARC as in the caseof the bilayer process. In the trilayer process, the resist bottom layeris required to have high etch resistance during substrate processingrather than the ARC function. Then a novolac resin containing morearomatic groups and having high etch resistance has been used as theresist bottom layer in the trilayer process.

FIG. 4 illustrates substrate reflectance with a change of the k value ofthe resist middle layer. It is seen that by setting a k value as low as0.2 or less and an appropriate thickness to the resist middle layer, asatisfactory antireflective effect as demonstrated by a substratereflectance of up to 1% is achievable. In general, the ARC film musthave a k value of 0.2 or greater in order to reduce reflectance to orbelow 1% at a film thickness of 100 nm or less (see FIG. 3). In thetrilayer resist structure wherein the resist bottom layer serves torestrain reflection to a certain extent, the resist middle layer mayhave an optimum k value of less than 0.2.

FIGS. 5 and 6 illustrate changes of reflectance with the varyingthickness of the resist middle layer and resist bottom layer, when theresist bottom layer has a k value of 0.2 and 0.6, respectively. Theresist bottom layer in FIG. 5 has a k value of 0.2 which assumedlycorresponds to the resist bottom layer optimized for the bilayerprocess, and the resist bottom layer in FIG. 6 has a k value of 0.6which is approximate to the k values at 193 nm of novolac andpolyhydroxystyrene. The thickness of the resist bottom layer varies withthe topography of the substrate whereas the thickness of the resistmiddle layer is kept substantially unchanged so that presumably it canbe coated to the predetermined thickness.

The resist bottom layer with a higher k value (0.6) is effective inreducing reflectance to 1% or less with a thinner film. In the eventthat the resist bottom layer has a k value of 0.2 and a thickness of 250nm, the resist middle layer must be increased in thickness in order toprovide a reflectance of 1% or less. Increasing the thickness of theresist middle layer is not preferable because a greater load is appliedto the resist film as the uppermost layer during dry etching of theresist middle layer.

FIGS. 5 and 6 illustrate reflection during dry exposure through anexposure tool having a lens with a NA of 0.85, indicating that byoptimizing the n and k values and thickness of the resist middle layerfor the trilayer process, a reflectance of up to 1% is achievableindependent of the k value of the resist bottom layer. Nevertheless,with the advance of the immersion lithography, the NA of the projectionlens increases beyond 1.0, and the angles of light entering not only theresist film, but also the underlying ARC film become smaller. The ARCfilm serves to control reflection due to the absorption of the filmitself and the offsetting effect by optical interference. Since obliquelight produces a less optical interference effect, reflection increases.Of the films in the trilayer process, it is the resist middle layer thatprovides reflection control by utilizing the optical interferenceeffect. The resist bottom layer is too thick to utilize the opticalinterference effect and lacks the anti-reflective function due to theoffsetting effect by optical interference. It is necessary to controlthe reflection from the surface of the resist bottom layer. To this end,the resist bottom layer must have a k value of less than 0.6 and an nvalue approximate to that of the overlying, resist middle layer. If afilm has a too small value of k and too high transparency, reflectionfrom the substrate also occurs, and a k value of about 0.25 to 0.48 isoptimum in the case of immersion lithography at NA 1.3. With respect tothe n value, a value approximate to the resist's n value of 1.7 is thetarget for both the middle and bottom layers.

Since benzene ring structure has very strong absorption, cresol novolacresins and polyhydroxystyrene resins containing the same have k valuesin excess of 0.6. Naphthalene ring structure is one of structures havinghigher transparency at wavelength 193 nm and higher etch resistance thanthe benzene ring. For example, JP-A 2002-014474 discloses a resistbottom layer comprising a naphthalene or anthracene ring. According tothe inventors' measurements, naphthol co-condensed novolac resin andpolyvinylnaphthalene resin have a k value between 0.3 and 0.4. Also thenaphthol co-condensed novolac resin and polyvinylnaphthalene resin havea low n value at wavelength 193 nm, specifically, the n value is 1.4 forthe naphthol co-condensed novolac resin and as low as 1.2 for thepolyvinylnaphthalene resin. Acenaphthylene polymers disclosed in JP-A2001-040293 and JP-A 2002-214777, for example, have a n value of 1.5 anda k value of 0.4 at 193 nm, close to the target values. There is a needfor a bottom layer having a high n value, a low k value, transparencyand high etch resistance. Notably JP-A 2010-122656 discloses a resistbottom layer material having a bisnaphthol group, the material having nand k values close to the target values, and improved etch resistance.

If the underlying processable substrate has steps, it is necessary todeposit a resist bottom layer to planarize the steps. By theplanarization of the resist bottom layer, a variation in thickness of anoverlying film, which may be a resist middle layer or a resist top layeror photoresist film, is minimized, and the focus margin of lithographycan be enlarged.

When an amorphous carbon bottom layer is formed by CVD using a reactantgas such as methane, ethane or acetylene gas, it is difficult to burysteps to be flat. On the other hand, when a resist bottom layer isformed by spin coating, there is a benefit that irregularities on thesubstrate can be buried. Suitable means for improving the buryingproperties of a material of coating type include the use of a novolacresin having a low molecular weight and a broad molecular weightdistribution as disclosed in JP-A 2002-047430 and a blend of a basepolymer and a low molecular weight compound having a low melting pointas disclosed in JP-A H11-154638.

It is known from SPIE vol. 469, p72 (1984) that novolac resins curethrough intermolecular crosslinking merely by heating. Reported thereinis a crosslinking mechanism by radical coupling that upon heating, aphenoxy radical generates from a phenolic hydroxyl group of cresolnovolac resin, and the radical migrates to methylene, a linking group ofthe novolac resin via resonance, whereby methylene moieties crosslinktogether. JP 3504247 discloses a pattern forming process using a bottomlayer having a carbon density which is increased by thermally induceddehydrogenation or dehydration condensation reaction of polycyclicaromatic compounds such as polyarylene, naphthol novolac, andhydroxyanthracene novolac.

A vitreous carbon film is formed by heating at or above 800° C. (seeGlass Carbon Bull. Chem. Soc. JPN, 41 (12) 3023-3024 (1968)). However,the upper limit of the temperature to which the wafer can be heated bythe lithography wafer process is up to 600° C., preferably up to 500° C.when thermal impacts like device damage and wafer deformation are takeninto account.

It is reported in Proc. of Symp. Dry. Process, p11 (2005) that as theprocessing line width is reduced, the resist bottom layer can be twistedor bowed when the processable substrate is etched using the resistbottom layer as mask. During etching of the substrate withfluorocarbon-based gas, a phenomenon occurs that hydrogen atoms in theresist bottom layer are replaced by fluorine atoms. As the surface ofthe resist bottom layer is converted to fluorocarbon-like, the bottomlayer increases its volume so that it may swell or lower its glasstransition temperature, allowing a finer pattern to be twisted. It isdescribed in the literature that twisting can be prevented by applying aresist bottom layer having a low hydrogen content. An amorphous carbonfilm formed by CVD is effective for preventing twist because thehydrogen content of the film can be minimized. However, the CVD has poorstep burying properties as pointed out above, and the CVD apparatus maybe difficult to introduce because of its price and footprint area. Ifthe twist problem can be solved by a bottom layer material from which afilm can be formed by coating, specifically spin coating, significantmerits would result from simplification of process and apparatus.

Also under study is a multilayer process in which a hard mask is formedon the resist bottom layer by the CVD technique. In the case ofsilicon-based hard masks (such as silicon oxide, silicon nitride, andsilicon oxynitride films) as well, inorganic hard masks formed by CVD orsimilar deposition techniques have more etch resistance than hard masksformed by the spin coating technique. In the event the processablesubstrate is a low-dielectric-constant film, the photoresist may bepoisoned therefrom (poisoning problem). The CVD film is more effectiveas a barrier film for preventing the poisoning problem.

Then a process involving forming a resist bottom layer by spin coatingfor planarization purpose, and forming an inorganic hard mask middlelayer as the resist middle layer by a CVD technique is investigated.When an inorganic hard mask middle layer, especially a nitride film, isformed by a CVD technique, the substrate must be heated at a temperatureof at least 300° C., typically about 400° C. Accordingly, when theresist bottom layer is formed by spin coating, the substrate must haveheat resistance at 400° C. Ordinary cresol novolac resins, naphtholnovolac resins, and even fluorene bisphenol resins known to be heatresistant fail to withstand heat at 400° C., experiencing a substantialfilm slimming after heating. There is a need for a resist bottom layerwhich can withstand heating at high temperature when an inorganic hardmask middle layer is formed by a CVD technique.

Because of the problem of film slimming or resin degradation afterheating due to shortage of heat resistance, heat treatment of a resistbottom layer material is usually carried out at or below 300° C.,typically 80 to 300° C. The heat treated film, however, still suffersfrom slimming after solvent treatment or twisting of the pattern duringetching of the substrate.

As discussed above, it would be desirable to have a method for forming aresist bottom layer which has optimum values of n and k as the ARC film,burying properties, etching resistance, and solvent resistance, and hassufficient heat resistance to withstand high temperature encounteredduring formation of an inorganic hard mask middle layer by a CVD orsimilar deposition technique, and prevents pattern twisting duringsubstrate etching.

CITATION LIST

-   -   Patent Document 1: JP-A H06-118651    -   Patent Document 2: JP-A H10-324748    -   Patent Document 3: JP-A H11-302382    -   Patent Document 4: JP-A 2002-055456    -   Patent Document 5: JP-A H09-110938    -   Patent Document 6: U.S. Pat. No. 6,506,497    -   Patent Document 7: U.S. Pat. No. 6,420,088    -   Patent Document 8: JP-A 2002-014474    -   Patent Document 9: JP-A 2001-040293    -   Patent Document 10: JP-A 2002-214777    -   Patent Document 11: JP-A 2010-122656    -   Patent Document 12: JP-A 2002-047430    -   Patent Document 13: JP-A H11-154638    -   Patent Document 14: JP 3504247    -   Non-Patent Document 1: SPIE Vol. 1925 (1993) p377    -   Non-Patent Document 2: SPIE Vol. 3333 (1998) p62    -   Non-Patent Document 3: Photopolymer Sci. and Technol. Vol. 9,        No. 3 (1996) p435-446    -   Non-Patent Document 4: SPIE Vol. 4345 (2001) p50    -   Non-Patent Document 5: J. Vac. Sci. Technol., 16(6),        November/December 1979    -   Non-Patent Document 6: SPIE Vol. 469 (1984) p72    -   Non-Patent Document 7: Glass Carbon Bull. Chem. Soc. JPN.        41 (12) 3023-3024 (1968)    -   Non-Patent Document 8: Proc. of Symp. Dry. Process, 2005, p11

SUMMARY OF INVENTION

An object of the present invention is to provide a naphthalenederivative and a method for preparing the same; an resist bottom layermaterial comprising the naphthalene derivative and useful to form aresist bottom layer in a multilayer resist film of at least three layersused in the lithography, the resist bottom layer being capable ofreducing reflectance, having etch resistance, heat resistance, andsolvent resistance, and being devoid of twist during etching of anunderlying substrate; a method for forming a resist bottom layer usingthe resist bottom layer material; and a pattern-forming process usingthe resist bottom layer material.

In one aspect, the invention provides a naphthalene derivative havingthe general formula (1).

Herein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, and n is such a natural number as to provide a weight averagemolecular weight of up to 100,000 as measured by GPC versus polystyrenestandards.

In a second aspect, the invention provides a naphthalene derivativecomprising a partial structure having the general formula (2).

Herein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering.

The naphthalene derivative comprising a partial structure having thegeneral formula (2) is typically obtained from dehydrating condensationreaction of a ketone compound having the following formula (3) with1,1′-bi-2-naphthol having the following formula (4) and a condensablecompound.

Herein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering. The condensable compound is selected from the group consisting ofbenzene, naphthalene, phenanthrene, anthracene, pyrene, biphenyl,phenylnaphthalene, phenylanthracene, phenylphenanthrene, phenylpyrene,binaphthyl, naphthylanthracene, naphthylphenanthrene, naphthylpyrene,bianthracene, anthracenylphenanthrene, anthracenylpyrene,biphenanthrene, phenanthrenylpyrene, bipyrene, diphenyl ether, phenylnaphthyl ether, phenyl anthracenyl ether, phenyl phenanthrenyl ether,phenyl pyrenyl ether, dinaphthyl ether, naphthyl anthracenyl ether,naphthyl phenanthrenyl ether, naphthyl pyrenyl ether, dianthracenylether, anthracenyl phenanthrenyl ether, anthracenyl pyrenyl ether,diphenanthrenyl ether, phenanthrenyl pyrenyl ether, and dipyrenyl ether,inclusive of various position isomers, a compound having the followingformula (4a):

wherein X is a single bond or a C₁-C₂₀ alkylene or aralkylene group, andm is 0 or 1, and substituted forms of the foregoing aromatic compoundsin which hydrogen is substituted by a halogen, monovalent C₁-C₂₀hydrocarbon, hydroxyl, C₁-C₂₀ alkoxy, nitro, or cyano group.

In a third aspect, the invention provides a method for preparing anaphthalene derivative having the following general formula (1),comprising effecting dehydrating condensation reaction of a ketonecompound having the following formula (3) with 1,1′-bi-2-naphthol havingthe following formula (4).

Herein Ar1, Ar2, and n are as defined above.

In a fourth aspect, the invention provides a method for preparing anaphthalene derivative comprising a partial structure having formula(2), said method comprising effecting dehydrating condensation reactionof a ketone compound having formula (3) with 1,1′-bi-2-naphthol havingformula (4) and a condensable compound. The condensable compound isselected from the above-defined group.

In a fifth aspect, the invention provides a resist bottom layer materialcomprising a naphthalene derivative as defined above or a polymercomprising recurring units of the naphthalene derivative as somerecurring units. The resist bottom layer material may further comprisean organic solvent, a crosslinker, and/or an acid generator.

In a sixth aspect, the invention provides a method for forming a resistbottom layer which is included in a multilayer resist film of at leastthree layers used in the lithography, comprising the steps of coatingthe resist bottom layer material defined above onto a substrate, andheat treating the coating of resist bottom layer material at atemperature of more than 100° C. to 600° C. for 10 to 600 seconds forcuring. Preferably, the step of coating the resist bottom layer materialonto a substrate is performed by spin coating.

In a still further aspect, the invention provides

a process for forming a pattern in a substrate by lithography,comprising at least the steps of forming a resist bottom layer on asubstrate by the method defined above, forming a resist middle layer onthe resist bottom layer using a silicon-containing resist middle layermaterial, forming a resist top layer on the resist middle layer using aresist top layer material which is a photoresist composition, exposing apattern circuit region of the resist top layer to radiation, developingthe resist top layer with a developer to form a resist pattern therein,etching the resist middle layer using the resist pattern as an etchingmask, etching the resist bottom layer using the resulting resist middlelayer pattern as an etching mask, and etching the substrate using theresulting resist bottom layer pattern as an etching mask;

a process for forming a pattern in a substrate by lithography,comprising at least the steps of forming a resist bottom layer on asubstrate by the method defined above, forming on the resist bottomlayer an inorganic hard mask middle layer which is selected from asilicon oxide film, silicon nitride film, and silicon oxynitride film,forming a resist top layer on the inorganic hard mask middle layer usinga resist top layer material which is a photoresist composition, exposinga pattern circuit region of the resist top layer to radiation,developing the resist top layer with a developer to form a resistpattern therein, etching the inorganic hard mask middle layer using theresist pattern as an etching mask, etching the resist bottom layer usingthe resulting inorganic hard mask middle layer pattern as an etchingmask, and etching the substrate using the resulting resist bottom layerpattern as an etching mask; or

a process for forming a pattern in a substrate by lithography,comprising at least the steps of forming a resist bottom layer on asubstrate by the method defined above, forming on the resist bottomlayer an inorganic hard mask middle layer which is selected from asilicon oxide film, silicon nitride film, and silicon oxynitride film,forming an organic ARC film on the inorganic hard mask middle layer,forming a resist top layer on the organic ARC film using a resist toplayer material which is a photoresist composition, exposing a patterncircuit region of the resist top layer to radiation, developing theresist top layer with a developer to form a resist pattern therein,etching the organic ARC film and inorganic hard mask middle layer usingthe resist pattern as an etching mask, etching the resist bottom layerusing the resulting inorganic hard mask middle layer pattern as anetching mask, and etching the substrate using the resulting resistbottom layer pattern as an etching mask.

Preferably, the step of forming an inorganic hard mask middle layer isperformed by CVD or ALD. Also preferably, the resist top layer materialis free of a silicon-containing polymer, and the step of etching theresist bottom layer using the middle layer pattern as an etching maskuses an oxygen or hydrogen-based etchant gas.

ADVANTAGEOUS EFFECTS OF INVENTION

Since the method for forming a resist bottom layer which is included ina multilayer resist film of at least three layers used in thelithography uses a resist bottom layer material comprising a naphthalenederivative having formula (1) or (2) or a polymer comprising recurringunits of the naphthalene derivative, the resulting resist bottom layerhas values of n and k optimum as ARC film, burying properties, improvedetch resistance, high heat resistance and solvent resistance, capable ofminimizing outgassing during bake, and being devoid of twist duringetching of an underlying substrate through a line pattern having a highaspect ratio and a width of less than 60 nm. When an inorganic hard maskis formed by CVD on the resist bottom layer which has been formed by aspin coating technique, the resist bottom layer has sufficient heatresistance to withstand the temperature treatment for forming theinorganic hard mask middle layer. A pattern forming process in which theresist bottom layer formed by spin coating is combined with theinorganic hard mask formed by CVD is available.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a trilayer resist working process,

FIGS. 1A through 1F showing steps of stacking and etching three layers.

FIG. 2 is a graph plotting the substrate reflectance versus bottom layerthickness in bilayer process when the k value of the bottom layer isfixed at 0.3 and the n value varies from 1.0 to 2.0.

FIG. 3 is a graph plotting the substrate reflectance versus bottom layerthickness in bilayer process when the n value of the bottom layer isfixed at 1.5 and the k value varies from 0 to 0.8.

FIG. 4 is a graph plotting the substrate reflectance in trilayer processwhen the bottom layer has a fixed n of 1.5, a fixed k of 0.6 and a fixedthickness of 500 nm, and the middle layer has a fixed n of 1.5, a kvalue varying from 0 to 0.3 and a thickness varying from 0 to 400 nm.

FIG. 5 is a graph plotting the substrate reflectance versus varyingthickness of the bottom layer and middle layer in trilayer process whenthe bottom layer has a fixed n of 1.5 and a fixed k of 0.2, and themiddle layer has a fixed n of 1.5 and a fixed k of 0.1.

FIG. 6 is a graph plotting the substrate reflectance versus varyingthickness of the bottom layer and middle layer in trilayer process whenthe bottom layer has a fixed n of 1.5 and a fixed k of 0.6, and themiddle layer has a fixed n of 1.5 and a fixed k of 0.1.

It is noted that the definition of complex index of refraction includesa refractive index (n) and an extinction coefficient (k).

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the disclosure, the singular forms “a,” “an” and “the” include pluralreferents unless the context clearly dictates otherwise. The notation(Cn-Cm) means a group containing from n to m carbon atoms per group.

The abbreviations and acronyms have the following meaning.

Mw: weight average molecular weight

Mn: number average molecular weight

Mw/Mn: molecular weight distribution or dispersity

GPC: gel permeation chromatography

PEB: post-exposure baking

ARC: antireflective coating

BARC: bottom antireflective coating

It is understood that for some structures represented by chemicalformulae, there can exist enantiomers and diastereomers. In such a case,a single formula collectively represents all such isomers. The isomersmay be used alone or in admixture. Notably, the enantiomer may containasymmetric carbon or be free of asymmetric carbon as in the case ofaxial chirality.

Naphthalene Derivative

In one embodiment of the invention, a naphthalene derivative has thegeneral formula (1).

Herein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, and n is such a natural number as to provide a weight averagemolecular weight (Mw) of up to 100,000 as measured by GPC versuspolystyrene standards.

In another embodiment, a naphthalene derivative possesses a partialstructure having the general formula (2).

Herein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering.

In formulae (1) and (2), each of Ar1 and Ar2 denotes a benzene ornaphthalene ring. Preferred examples of the partial structure:

include the following partial structures.

Inter alia, fluorene and benzofluorene ring structures are morepreferred. In these groups, a hydrogen atom may be replaced by a halogenatom, hydrocarbon, hydroxyl, alkoxy, nitro, cyano group or the like.

In the partial structure, the bond positions of a group of the formula:

to the binaphthol structure are preferably the bond positions in thefollowing general formulae, that is, 6- and 6′-positions in1,1′-bi-2-naphthol, but not limited thereto.

In formula (1), n is such a natural number as to provide a molecularweight less than or equal to 100,000. The naphthalene derivativecomprising a partial structure of formula (2) desirably has an overallmolecular weight of less than or equal to 100,000. As used herein, theterm “molecular weight” is as measured by GPC versus polystyrenestandards. Specifically n is such a natural number as to provide aweight average molecular weight (Mw) of less than or equal to 100,000,preferably 700 to 50,000, and more preferably 2,000 to 30,000. Whensynthesized by condensation reaction or the like, the naphthalenederivative is available as a mixture of derivatives having varyingvalues of n, that is, having a molecular weight distribution. Thenaphthalene derivative comprising a partial structure of formula (2)preferably has a molecular weight in the above-described range as well.

The method for preparing the naphthalene derivative having formula (1)is characterized by dehydration condensation reaction of a ketonecompound (3) with 1,1′-bi-2-naphthol (4), as shown below.

Usually the reaction may be conducted in a solventless system or in asolvent in the presence of an acid or base catalyst at room temperatureor optionally under cooling or heating. Examples of the solvent usedherein include alcohols such as methanol, ethanol, isopropyl alcohol,butanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol,ethylene glycol monomethyl ether, and propylene glycol monomethyl ether;ethers such as diethyl ether, dibutyl ether, diethylene glycol diethylether, diethylene glycol dimethyl ether, tetrahydrofuran, and1,4-dioxane; chlorinated solvents such as methylene chloride,chloroform, dichloroethane, and trichloroethylene; hydrocarbons such ashexane, heptane, benzene, toluene, xylene, and cumene; nitriles such asacetonitrile; ketones such as acetone, ethyl methyl ketone, and isobutylmethyl ketone; esters such as ethyl acetate, n-butyl acetate, andpropylene glycol methyl ether acetate (PGMEA); and aprotic polarsolvents such as dimethyl sulfoxide, N,N-dimethylformamide, andhexamethylphosphoric triamide, which may be used alone or in admixtureof two or more. Examples of the acid catalyst used herein includemineral acids such as hydrochloric acid, hydrobromic acid, sulfuricacid, nitric acid, phosphoric acid, and heteropoly-acid; organic acidssuch as oxalic acid, trifluoroacetic acid, methanesulfonic acid,benzenesulfonic acid, p-toluenesulfonic acid, andtrifluoromethanesulfonic acid; and Lewis acids such as aluminumtrichloride, aluminum ethoxide, aluminum isopropoxide, borontrifluoride, boron trichloride, boron tribromide, tin tetrachloride, tintetrabromide, dibutyltin dichloride, dibutyltin dimethoxide, dibutyltinoxide, titanium tetrachloride, titanium tetrabromide, titanium(IV)methoxide, titanium(IV) ethoxide, titanium(IV) isopropoxide, andtitanium(IV) oxide. Examples of the base catalyst used herein includeinorganic bases such as sodium hydroxide, potassium hydroxide, bariumhydroxide, sodium carbonate, sodium hydrogen carbonate, potassiumcarbonate, lithium hydride, sodium hydride, potassium hydride, andcalcium hydride; alkyl metals such as methyllithium, n-butyllithium,methylmagnesium chloride, and ethylmagnesium bromide; alkoxides such assodium methoxide, sodium ethoxide, and potassium t-butoxide; and organicbases such as triethylamine, diisopropylethylamine, N,N-dimethylaniline,pyridine, and 4-dimethylaminopyridine. The reaction temperature ispreferably from −50° C. to near the boiling point of the solvent, morepreferably from room temperature to 100° C.

The method for preparing the naphthalene derivative having a partialstructure of formula (2) may be arrived at by introducing a condensablecompound in the method for preparing the naphthalene derivative offormula (1), that is, dehydration condensation reaction of ketonecompound (3) with 1,1′-bi-2-naphthol (4).

Suitable condensable compounds which can be co-present during thereaction include aromatic hydrocarbons and aromatic compounds having anoxygen functional group, for example, position isomers of aromaticcompounds in which hydrogen is substituted by halogen, hydrocarbon,hydroxyl, alkoxy, nitro, cyano or the like, such as benzene,naphthalene, phenanthrene, anthracene, pyrene, biphenyl,phenylnaphthalene, phenylanthracene, phenylphenanthrene, phenylpyrene,binaphthyl, naphthylanthracene, naphthylphenanthrene, naphthylpyrene,bianthracene, anthracenylphenanthrene, anthracenylpyrene,biphenanthrene, phenanthrenylpyrene, and bipyrene; and position isomersof aromatic ethers in which hydrogen on the aromatic moiety issubstituted by halogen, hydrocarbon, hydroxyl, alkoxy, nitro, cyano orthe like, such as diphenyl ether, phenyl naphthyl ether, phenylanthracenyl ether, phenyl phenanthrenyl ether, phenyl pyrenyl ether,dinaphthyl ether, naphthyl anthracenyl ether, naphthyl phenanthrenylether, naphthyl pyrenyl ether, dianthracenyl ether, anthracenylphenanthrenyl ether, anthracenyl pyrenyl ether, diphenanthrenyl ether,phenanthrenyl pyrenyl ether, and dipyrenyl ether. Preferred examplesinclude biphenols having a phenolic hydroxyl group such as2,2′-biphenol, 2,4′-biphenol, and 4,4′-biphenol; hydroxyphenylnaphthols;binaphthols such as 6,6′-bi-2,2′-naphthol, 1,6′-bi-2,2′-naphthol, and4,4′-bi-1,1′-naphthol; dihydroxynaphthalenes such as1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene,1,4-dihydroxynaphthalene, 1,5-dihydroxynaphthalene,1,6-dihydroxynaphthalene, 1,7-dihydroxynaphthalene,1,8-dihydroxynaphthalene, 2,3-dihydroxynaphthalene,2,6-dihydroxynaphthalene, and 2,7-dihydroxynaphthalene; dinaphthylethers such as 1,1′-dinaphthyl ether, 1-naphthyl 2-naphthyl ether, and2,2′-dinaphthyl ether; and dialkoxynaphthalenes such as1,2-dimethoxynaphthalene, 1,3-dimethoxynaphthalene,1,4-dimethoxynaphthalene, 1,5-dimethoxynaphthalene,1,6-dimethoxynaphthalene, 1,7-dimethoxynaphthalene,1.8-dimethoxynaphthalene, 2,3-dimethoxynaphthalene,2,6-dimethoxynaphthalene, and 2,7-dimethoxynaphthalene. Also useful arecompounds having the following formula (4a):

wherein X is a single bond or a C₁-C₂₀ alkylene or aralkylene group, andm is 0 or 1.

Examples of the compound (4a) are given below.

Of the foregoing condensable compounds, preference is given to thedinaphthyl ether, dinaphthofuran, dinaphthopyrane,14-alkyl-14-H-dibenzoxanthene, and 14-aryl-14-H-dibenzoxanthenestructures.

Described below is the design concept of the naphthalene derivativehaving formula (1) or (2). The naphthalene derivative having formula (1)or (2) is used to formulate a material for forming a resist bottom layerwhich is included in a multilayer resist film of at least three layersused in the lithography. As mentioned above, a film having a high carbonatom density and a low hydrogen atom density is necessary to establishthe properties required for the resist bottom layer, including etchresistance, heat resistance, and anti-twisting during substrate etching.Then the bottom layer material should desirably have a high carbon atomdensity and a low hydrogen atom density.

One exemplary naphthalene derivative used in a resist bottom layer forcomparison purposes is a 2-naphthol/fluorenone condensate having formula(5) below, also known as bisnaphthol fluorene (referred to as compound(5), hereinafter), as disclosed in JP-A 2007-99741. One known means forconverting compound (5) into a high molecular weight compound is novolacformation. A novolac resin formed using formaldehyde is, for example, aresin comprising recurring units having formula (5′) (referred to asresin (5′), hereinafter).

Herein n is a natural number.

As compared with compound (5) or resin (5′), naphthalene derivative (1)of the invention has many structural advantages. The same applies tonaphthalene derivative (2) of the invention.

-   [1] Since the present naphthalene derivative (1) has a structure    that is obtained by eliminating hydrogen (H₂) from the naphthol    units of compound (5) to form a carbon-carbon bond, the carbon    density of the resin becomes higher by the value of hydrogen    eliminated.-   [2] Compound (5), which is a monomer, must be converted into a high    molecular weight compound or polymer by novolac formation or    suitable means before it can be used as a bottom layer material. The    present naphthalene derivative is already a polymer due to    carbon-carbon bonds and ready for use as a resin without a need for    further polymerization such as novolac formation.-   [3] While novolac form resin (5′) has a reduced carbon density (or    increased hydrogen density) due to novolac crosslink —CH₂—, the    present naphthalene derivative is free of such disadvantage.-   [4] If necessary, intermolecular crosslinks may be introduced into    the present naphthalene derivative by novolac formation with a    polycondensable monomer or suitable means.

Improved properties of the bottom layer film attributable to theseadvantages [1] to [4] will be demonstrated in Examples.

-   [5] Upon the formation of a bottom layer film by heating, the    following five-ring formation reaction due to the dehydration of the    present naphthalene derivative may occur, thereby further improving    a carbon density.

Another exemplary naphthalene derivative used in a resist bottom layerfor comparison purposes is a resin comprising recurring units havingformula (5″) below (referred to as resin (5″), hereinafter), which isobtained by oxidative coupling reaction of compound (5) into a polymer.This resin is described, for example, in JP-A 2010-122656 correspondingto US 2010/099044 A1 although they lack the detailed description ofpreparation conditions.

Herein n is a natural number.

Like the present naphthalene derivative (1), resin (5″) has a structurethat is obtained by eliminating hydrogen (H₂) from the naphthol units ofcompound (5) to form a carbon-carbon bond. Accordingly, the carbondensity of resin (5″) is higher by the value of hydrogen eliminated.However, resin (5″) has some disadvantages. First, the oxidativecoupling reaction of monomeric compound (5) into a polymer needs aspecial metal catalyst and heating at a high temperature in the presenceof air or oxygen. These reaction conditions are not suited in theapplication where metal contamination should be avoided. The hightemperature causes unwanted cleavage of carbon-carbon bonds and hence,degradation. The process is thus difficult to carry out in acommercially acceptable manner. It is very awkward to drive theoxidative coupling reaction to completion. In contrast, the method ofpreparing the present naphthalene derivative starts with commerciallyavailable 1,1′-bi-2-naphthol (4) which is an oxidative coupling dimer of2-naphthol, and converts it into a polymer, overcoming the aboveproblem. Secondly, while the naphthol unit is considered to serve as afunctional/reactive site in dissolution in a formulating solvent, filmformation, and heat curing in the bottom layer application, the presentnaphthalene derivative (1) contains fluorene derivative and naphthol ina ratio of n:2n+2, and resin (5″) contains them in a ratio of n:2n. Thepresent naphthalene derivative (1) permits the naphthol density permolecular weight unit to be increased independent of the value of n.Thirdly, in case of considering the above-mentioned five-ring formationreaction due to the dehydration, all the hydroxy groups of the presentnaphthalene derivative (1) has the possibility of contributing thefive-ring formation reaction due to the dehydration. On the other hand,it is thought that the resin (5″) has the disadvantage since the hydroxygroups at the both ends of the resin (5″) does not structurallycontribute the five-ring formation reaction due to the dehydration andthus the improvement of a carbon density is not expected.

The present naphthalene derivative (1) or (2) may be subjected topolycondensation with a polycondensable monomer to form a polymer, whichmay be used as the resist bottom layer material. Suitablepolycondensable monomers used herein include unsaturated hydrocarbonssuch as indene, acenaphthylene, biphenyl, dicyclopentadiene,tetrahydroindene, 4-vinylcyclohexene, norbornadiene,5-vinylnorborn-2-ene, α-pinene, β-pinene, and limonene; phenols andnaphthols such as phenol, o-cresol, m-cresol, p-cresol,2,3-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol,3,5-dimethylphenol, 2,4-dimethylphenol, 2,6-dimethylphenol,2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2-t-butylphenol,3-t-butylphenol, 4-t-butylphenol, 2-phenylphenol, 3-phenylphenol,4-phenylphenol, 3,5-diphenylphenol, 2-naphthylphenol, 3-naphthylphenol,4-naphthylphenol, 4-tritylphenol, resorcinol, 2-methylresorcinol,4-methylresorcinol, 5-methylresorcinol, catechol, 4-t-butylcatechol,2-methoxyphenol, 3-methoxyphenol, 2-propylphenol, 3-propylphenol,4-propylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol,2-methoxy-5-methylphenol, 2-t-butyl-5-methylphenol, pyrogallol, thymol,isothymol, 1-naphthol, 2-naphthol, 2-methyl-1-naphthol,4-methoxy-l-naphthol, 7-methoxy-2-naphthol, 1,5-dihydroxynaphthalene,1,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene,2,6-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, methyl3-hydroxynaphthalene-2-carboxylate, 4-tritylphenol, hydroxyanthracene,dihydroxyanthracene, trihydroxyanthracene, hydroxypyrene, bisphenol, andtrisphenol as well as hydroxyindene; hetero-aromatics containing oxygensuch as benzofuran, and fluorene-phenol condensates such as4,4′-bisphenol fluorene and 6,6′-bisnaphthol fluorene. In thesecompounds, hydrogen may be substituted by halogen, hydrocarbon,hydroxyl, alkoxy, nitro, cyano group or the like. Ternary ormulti-component copolymers may be used as well.

One exemplary means for converting naphthalene derivative (1) or (2) toa higher molecular weight compound through polycondensation with apolycondensable monomer is novolac formation through condensation with amonomer, which is described below. The novolac forming reaction uses analdehyde, examples of which include formaldehyde, trioxan,paraformaldehyde, acetaldehyde, benzaldehyde, propionaldehyde,phenylacetaldehyde, α-phenylpropionaldehyde, β-phenylpropionaldehyde,1-naphthaldehyde, 2-naphthaldehyde, and furfural. These aldehydecompounds may be substituted with one or more halogen atom, hydrocarbon,hydroxyl, alkoxy, nitro, cyano group or the like. Of these, formaldehydeand equivalents, benzaldehyde, 1-naphthaldehyde, 2-naphthaldehyde, andsubstituted forms of the foregoing are preferred. These aldehydecompounds may be used alone or in admixture of two or more.

The novolac forming reaction may be effected in the presence of acatalyst. Acid catalysts are preferred. Examples of the acid catalystused herein include mineral acids such as hydrochloric acid, hydrobromicacid, sulfuric acid, nitric acid, phosphoric acid, and heteropoly-acid;organic acids such as oxalic acid, trifluoroacetic acid, methanesulfonicacid, benzenesulfonic acid, p-toluenesulfonic acid, andtrifluoromethanesulfonic acid; and Lewis acids such as aluminumtrichloride, aluminum ethoxide, aluminum isopropoxide, borontrifluoride, boron trichloride, boron tribromide, tin tetrachloride, tintetrabromide, dibutyltin dichloride, dibutyltin dimethoxide, dibutyltinoxide, titanium tetrachloride, titanium tetrabromide, titanium(IV)methoxide, titanium(IV) ethoxide, titanium(IV) isopropoxide, andtitanium(IV) oxide. Inter alia, acidic catalysts such as hydrochloricacid, sulfuric acid, nitric acid, formic acid, oxalic acid, acetic acid,methanesulfonic acid, camphorsulfonic acid, p-toluenesulfonic acid, andtrifluoromethanesulfonic acid are preferred. Reaction may be conductedby charging monomers, aldehyde compound and catalyst all at once, or byadding dropwise any selected component. At the end of reaction, theunreacted reactants, catalyst and the like are removed from the reactionsystem. To this end, the reactor may be heated to a temperature of 130to 230° C. under a vacuum of 1 to 50 mmHg for removing any volatiles.

The polycondensed resin preferably has a Mw of 1,000 to 200,000, morepreferably 2,000 to 50,000, as measured versus polystyrene standards,and a dispersity (Mw/Mn) in the range of 1.2 to 7. It is preferred thatthe molecular weight distribution of the resin is narrowed by cuttingoff the monomeric and oligomeric components and low-molecular weightfractions having a Mw of up to 1,000, because the crosslinkingefficiency is increased and the content of volatile components duringbake is minimized to prevent contamination around the bake cup.

Also, a fused aromatic or alicyclic substituent group may be introducedinto the naphthalene derivative having formula (1) or (2) or a polymercomprising the same as some recurring units. Examples of the substituentgroup which can be introduced herein are given below.

Of these, polycyclic aromatic groups such as anthracenemethyl andpyrenemethyl are most preferred for exposure at 248 nm. A substituentgroup having an alicyclic or naphthalene structure is preferably usedfor improved transparency at 193 nm. On the other hand, since thebenzene ring has a window for improved transparency at wavelength 157nm, absorption must be increased by shifting the absorption wavelength.The furan ring has absorption at a shorter wavelength than the benzenering, and thus exhibits slightly improved absorption at 157 nm, with itseffect being faint. The naphthalene, anthracene and pyrene rings exhibitenhanced absorption due to a shift of absorption wavelength to thelonger side. Since these aromatic rings have the additional advantage ofimproved etch resistance, they are preferred for use. The method ofintroducing the foregoing substituent group is, for example, byintroducing an alcohol compound having a hydroxyl group at the sitewhere the substituent group is attached into the naphthalene derivativehaving formula (1) or (2) or a polymer comprising the same as somerecurring units in the presence of an acid catalyst.

Suitable acid catalysts are as exemplified above for the novolac formingreaction. Introduction of a substituent group may be conductedconcurrently with the novolac forming reaction.

To improve transparency at 193 nm, the naphthalene derivative havingformula (1) or (2) or the polymer comprising the same as some recurringunits may be hydrogenated. A degree of hydrogenation is preferably up to80 mol %, more preferably up to 60 mol % based on the aromatic group.

The naphthalene derivative having formula (1) or (2) or the polymercomprising the same as some recurring units (generally referred to as“inventive compound,” hereinafter) may be used as a resist bottom layermaterial in the method for forming a resist bottom layer in the trilayerprocess. These inventive compounds have very high heat resistancebecause of inclusion of quaternary carbon and a carbon density which isas high as approximately 90%. When a hard mask in the form of a siliconoxide, silicon nitride or silicon oxynitride film is formed on theresist bottom layer by CVD or similar deposition technique, a hightemperature, specifically a temperature above 300° C. in the case ofnitride film is necessary, and the resist bottom layer is thus requiredto have high heat resistance. Since the inventive compounds are benzenering fused hydrocarbons, they exhibit relatively low absorption atwavelength 193 nm due to an absorption shift, and are expected to exertbetter antireflective effect at a film thickness of at least 100 nm whenused in the trilayer process. Also, the inventive compounds have higherresistance against CF₄/CHF₃ gas and Cl₂/BCl₃ gas etching used insubstrate processing than ordinary m-cresol novolac resins. Since thecount of hydrogen atoms becomes smaller by an increment of the aromaticcount, etch resistance is improved, and the occurrence of pattern twistduring substrate etching is suppressed. By baking at a temperature inexcess of 300° C., the bottom layer is endowed with more etch resistanceand solvent resistance and the occurrence of pattern twist duringsubstrate etching is suppressed.

Bottom Layer Material

The resist bottom layer material used in the method for forming a resistbottom layer in the trilayer process is defined as comprising (A) thenaphthalene derivative having formula (1) or (2) or the polymercomprising the same as some recurring units, as an essential componentand preferably (B) an organic solvent. If it is desired to improve spincoating properties and substrate step burying property as well as therigidity and solvent resistance of the film, the material may furthercomprise (C) a blending compound or polymer, (D) a crosslinker, and (E)an acid generator.

The organic solvent (B) used in the bottom layer material may be anydesired one as long as components (A) to (E) and other components aredissolvable therein. Suitable solvents which can be added are describedin JP-A 2008-65303 corresponding to US 2008/038662 A1: paragraphs [0190]to [0191]. In a preferred embodiment, the resist bottom layer materialcomprises organic solvent (B), and in a more preferred embodiment, itfurther comprises crosslinker (D) and acid generator (E) if it isdesired to improve spin coating properties and substrate step buryingproperty as well as the rigidity and solvent resistance of the film.

Optionally, another polymer or compound may be blended as base polymer(C). When the blending compound or polymer is blended with thenaphthalene derivative having formula (1) or (2) or the polymercomprising the same as some recurring units, it can serve the functionsof improving film formation by spin coating and burying in steppedsubstrates. More preferably a choice may be made of materials having ahigh carbon density and etching resistance. Suitable blending polymersinclude novolac resins derived from phenol, o-cresol, m-cresol,p-cresol, 2,3-dimethylphenol, 2,5-dimethylphenol, 3,4-dimethylphenol,3,5-dimethylphenol, 2,4-dimethylphenol, 2,6-dimethylphenol,2,3,5-trimethylphenol, 3,4,5-trimethylphenol, 2-t-butylphenol,3-t-butylphenol, 4-t-butylphenol, 2-phenylphenol, 3-phenylphenol,4-phenylphenol, 3,5-diphenylphenol, 2-naphthylphenol, 3-naphthylphenol,4-naphthylphenol, 4-tritylphenol, resorcinol, 2-methylresorcinol,4-methylresorcinol, 5-methylresorcinol, catechol, 4-t-butylcatechol,2-methoxyphenol, 3-methoxyphenol, 2-propylphenol, 3-propylphenol,4-propylphenol, 2-isopropylphenol, 3-isopropylphenol, 4-isopropylphenol,2-methoxy-5-methylphenol, 2-t-butyl-5-methylphenol, pyrogallol, thymol,isothymol, 4,4′-(9H-fluoren-9-ylidene)bisphenol,2,2′-dimethyl-4,4′-(9H-fluoren-9-ylidene)bisphenol,2,2′-diallyl-4,4′-(9H-fluoren-9-ylidene)bisphenol,2,2′-difluoro-4,4′-(9H-fluoren-9-ylidene)bisphenol,2,2′-diphenyl-4,4′-(9H-fluoren-9-ylidene)bisphenol,2,2′-dimethoxy-4,4′-(9H-fluoren-9-ylidene)bisphenol,2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol,3,3,3′,3′-tetramethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol,3,3,3′,3′,4,4′-hexamethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol,2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-5,5′-diol,5,5′-dimethyl-3,3,3′,3′-tetramethyl-2,3,2′,3′-tetrahydro-(1,1′)-spirobiindene-6,6′-diol,1-naphthol, 2-naphthol, 2-methyl-1-naphthol, 4-methoxy-1-naphthol,7-methoxy-2-naphthol, and dihydroxynaphthalenes such as1,5-dihydroxynaphthalene, 1,7-dihydroxynaphthalene and2,6-dihydroxynaphthalene, methyl 3-hydroxy-naphthalene-2-carboxylate,indene, hydroxyindene, benzofuran, hydroxyanthracene, acenaphthylene,biphenyl, bisphenol, trisphenol, dicyclopentadiene, tetrahydroindene,4-vinylcyclohexene, norbornadiene, 5-vinylnorborn-2-ene, α-pinene,β-pinene, limonene, etc.; and polyhydroxystyrene, polystyrene, polyvinylnaphthalene, polyvinyl anthracene, polyvinyl carbazole, polyindene,polyacenaphthylene, polynorbornene, polycyclodecene,polytetracyclododecene, polynortricyclene, poly(meth)acrylate, andcopolymers thereof. Also included are nortricyclene as described in JP-A2004-205658, hydrogenated naphthol novolac resins as described in JP-A2004-205676, naphthol dicyclopentadiene copolymers as described in JP-A2004-205685, phenol dicyclopentadiene copolymers as described in JP-A2004-354554 (US 2004/241577 A1) and JP-A 2005-010431 (US 2004/259037A1), fluorene bisphenol novolac resins as described in JP-A 2005-128509(US 2006/019195 A1), acenaphthylene copolymers as described in JP-A2005-250434, indene copolymers as described in JP-A 2006-53543 (US2006/014106 A1), phenol-containing fullerene as described in JP-A2006-227391, bisphenol compounds and novolac resins thereof as describedin JP-A 2006-259249, JP-A 2006-293298 (US 2006/204891 A1), and JP-A2007-316282 (US 2007/275325 A1), dibisphenol compounds and novolacresins thereof as described in JP-A 2006-259482, novolac resins ofadamantane phenol compounds as described in JP-A 2006-285095,hydroxyvinyl naphthalene copolymers as described in JP-A 2007-171895 (US2007/122740 A1), bisnaphthol compounds and novolac resins thereof asdescribed in JP-A 2010-122656 (US 2010/099044 A1), ROMP polymers asdescribed in JP-A 2008-026600, tricyclopentadiene copolymers andanalogous resins as described in JP-A 2008-096684, and fullerene resinsas described in JP-A 2006-227391 and JP-A 2008-158002.

The amount of the blending compound or polymer compounded is usually 0to 1,000 parts by weight, preferably 0 to 500 parts by weight per 100parts by weight of the naphthalene derivative having formula (1) or (2)or the polymer comprising the same as some recurring units.

One of the functions required for the resist bottom layer additionallyhaving an antireflective function is the elimination of intermixing withthe overlying films (i.e., silicon-containing resist middle layer andresist top layer) and the elimination of diffusion of low molecularweight components into the overlying films (see Proc. SPIE Vol. 2195,p225-229 (1994)). One common means for preventing intermixing anddiffusion is by baking an antireflective film as spin coated forinducing thermal crosslinkage. Then, in the event the antireflectivefilm material contains a crosslinker, a method of introducingcrosslinkable substituent groups into the polymer may be employed. Evenwhen a particular crosslinker is not added, the naphthalene derivativehaving formula (1) or (2) or the polymer comprising the same undergoescrosslinkage through the reaction mechanism (to be described later) byheating at a temperature in excess of 300° C.

Since the naphthalene derivative having formula (1) or (2) or thepolymer comprising the same as some recurring units has very high heatresistance, it undergoes substantially no pyrolysis even when baked at ahigh temperature in excess of 300° C. Since baking at a temperature inexcess of 300° C. promotes evaporation of the solvent, the film of theinventive compound tends to increase its carbon density and denseness,exhibiting more etch resistance. It is thought that the improvement ofthe carbon density based on the above-mentioned five-ring formationreaction due to the dehydration is contributed to the improvement of theetch resistance. In addition, baking at a temperature in excess of 300°C. endows the film with more solvent resistance and prevents the filmfrom being twisted during substrate etching. When a less heat resistantmaterial film is baked at a high temperature in excess of 300° C., thefilm does not always increase its carbon density, because of possiblepyrolysis, and may be degraded in some cases.

Suitable crosslinkers which can be used herein are described in JP-A2008-65303 (US 2008/038662 A1: paragraphs [0122] to [0126]).

An acid generator may be added to the resist bottom layer material tofurther accelerate the thermally induced crosslinking reaction. Acidgenerators include those which generate an acid through pyrolysis andthose which generate an acid upon exposure to light, and both areuseful. The acid generators used herein include those described in JP-A2008-65303 (US 2008/038662 A1: paragraphs [0128] to [0179]).

In the resist bottom layer material, a basic compound may be compoundedfor improving the storage stability. The basic compound plays the roleof an acid quencher for preventing a minute amount of an acid generatedby the acid generator from facilitating crosslinking reaction. The basiccompound which can be added herein may be any of the compounds describedin JP-A 2008-65303 (US 2008/038662 A1: paragraphs [0180] to [0189]).

A surfactant may be added to the resist bottom layer material forimproving the applicability by spin coating. Suitable surfactants aredescribed in JP-A 2008-111103 (US 2008/118860 A1: paragraphs [0158] to[0159]).

Process

It is now described how to form a pattern using the resist bottom layermaterial of the invention.

Like photoresists, the resist bottom layer material of the invention canbe applied onto a processable substrate by any desired technique such asspin coating, to form a bottom layer thereon. Spin coating and othercoating techniques are effective for burying steps. After spin coating,the coating is desirably baked in order to evaporate off the solvent andto promote crosslinking reaction for preventing the bottom layer fromintermixing with the resist middle layer and top layer to besubsequently applied thereon. The bake is preferably effected at atemperature of more than 100° C. to 600° C., more preferably 250° C. to500° C. for a time of 10 to 600 seconds, more preferably 10 to 300seconds. With thermal impacts such as device damages and waferdeformation taken into account, the upper limit of permissible heatingtemperature in the lithographic wafer process is up to 600° C.,preferably up to 500° C.

As understood from SPIE Vol. 469, p72 (1984), cited above, when thenaphthalene derivative having formula (1) or the polymer comprising thesame used in the method for forming a resist bottom layer according tothe invention is heated, radicals are created, helping crosslinkingreaction take place. Since this reaction is a radical reaction in whichno molecules are eliminated, the material film does not undergoshrinkage due to crosslinking as long as the material is fully heatresistant.

Although the bake atmosphere may be air, it is sometimes preferred forpreventing the resist bottom layer from oxidation to introduce an inertgas such as N₂, Ar or He into the atmosphere for reducing the oxygencontent. Where it is necessary to control the oxygen concentration forpreventing oxidation, the oxygen concentration is preferably up to 1,000ppm, more preferably up to 100 ppm. It is preferred to prevent theresist bottom layer from oxidation during bake because oxidation cancause an increase of absorption or a drop of etch resistance. On theother hand, bake in air or oxygen-rich gas is sometimes preferable whenmolecular crosslinking by oxidative coupling is intended.

The thickness of the resist bottom layer may be suitably determinedalthough it is preferably in the range of 30 to 20,000 nm, especially 50to 15,000 nm. After the resist bottom layer is formed, asilicon-containing resist middle layer and a silicon-free resist toplayer are formed thereon in the case of the trilayer process.

According to the process of the invention, a pattern is formed bycoating a substrate with the resist bottom layer material comprising thenaphthalene derivative having formula (1) or (2) or the polymercomprising the same as some recurring units to form a resist bottomlayer thereon, forming a resist top layer of a photoresist compositionon the resist bottom layer via an intervening resist middle layer,exposing a predetermined region of the resist top layer to radiation orthe like, developing the resist top layer with a developer to form aresist pattern, etching the resist middle layer using the resist patternas mask, and etching the resist bottom layer and the substrate using theresulting resist middle layer pattern as mask.

In the embodiment wherein the inorganic hard mask middle layer is formedon the resist bottom layer, a silicon oxide film, silicon nitride filmor silicon oxynitride (SiON) film is formed by chemical vapor deposition(CVD) or atomic layer deposition (ALD). The formation of nitride film isdescribed in JP-A 2002-334869 and WO 2004/066377. The inorganic hardmask typically has a thickness of 5 to 200 nm, preferably 10 to 100 nm.The most preferred inorganic hard mask is a SiON film which is fullyeffective as an ARC. Since the substrate reaches a temperature of 300 to500° C. during deposition of a SiON film, the bottom layer mustwithstand a temperature of 300 to 500° C. Since the resist bottom layermaterial comprising the naphthalene derivative having formula (1) or (2)or the polymer comprising the same as some recurring units has heatresistance sufficient to withstand a temperature of 300 to 500° C., itis possible to combine a resist bottom layer formed by spin coating withan inorganic hard mask formed by CVD or ALD.

In one embodiment, a photoresist film is formed on the resist middlelayer as the resist top layer. In another embodiment, an organicantireflective coating film (BARC) is formed on the resist middle layerby spin coating, and a photoresist film formed thereon. Where the resistmiddle layer is a SiON film, an antireflective film consisting of twolayers, SiON and BARC films functions to suppress reflection even in theimmersion lithography with a high NA in excess of 1.0. Another advantagearising from formation of BARC is to reduce footing of the photoresistpattern immediately above SiON.

Also preferred as the silicon-containing resist middle layer in thetrilayer process is a middle layer based on polysilsesquioxane.Reflection may be suppressed by endowing the resist middle layer withthe ARC function. Suitable silsesquioxane-based silicon compounds aredescribed, for example, in JP-A 2004-310019, 2005-015779, 2005-018054,2005-352104, 2007-065161, 2007-163846, 2007-226170, and 2007-226204.Particularly for 193 nm exposure, when an aromatic rich material havinghigh resistance to substrate etching is used as the resist bottom layer,that resist bottom layer has a high value of k and allows high substratereflection. However, if reflection can be suppressed by the resistmiddle layer, then totally the substrate reflection can be suppressed toor below 0.5%. Preferred as the resist middle layer capable ofsuppressing reflection is anthracene for the 248 nm and 157 nmexposures, or polysilsesquioxane having a pendant in the form of aphenyl or photo-absorptive group having a silicon-silicon bond andcapable of acid or heat-induced crosslinking for the 193 nm exposure.The resist middle layer preferably has a thickness of 7 to 200 nm.

For forming the silicon-containing resist middle layer, spin coating issimple and cost effective as compared with CVD.

The resist top layer in the trilayer resist film may be either positiveor negative and may be any of commonly used photoresist compositions.When the photoresist composition is applied to form a single-layerresist top layer, a spin coating technique is preferably used as in thecase of the resist bottom layer. The photoresist composition is spincoated and then pre-baked, preferably at 60 to 180° C. for 10 to 300seconds. Thereafter, the resist layer is routinely exposed to radiationthrough a desired pattern, post-exposure baked (PEB) and developed witha developer, obtaining a resist pattern. The thickness of the resist toplayer is preferably in a range of 30 to 500 nm, more preferably 50 to400 nm, though not particularly limited. The radiation for exposure maybe selected from among high-energy radiation having a wavelength of upto 300 nm, specifically excimer laser beams of 248 nm, 193 nm and 157nm, soft X-ray (EUV) of 3 to 20 nm, electron beam (EB), and X-ray.

Next, etching is carried out using the resist pattern as mask. In thetrilayer process, the resist middle layer, specifically inorganic hardmask is etched with fluorocarbon-base gas using the resist pattern asmask. Then the resist bottom layer is etched with oxygen or hydrogen gasusing the resist middle layer pattern, specifically inorganic hard maskpattern as mask.

Next, the processable substrate is etched by a standard technique. Forexample, when the substrate is SiO₂, SiN or silica-baselow-dielectric-constant insulating film, etching with afluorocarbon-base gas is employed. When the substrate is p-Si, Al or W,etching with a chlorine or bromine-base gas is employed. When thesubstrate processing is etching with a fluorocarbon-base gas, thesilicon-containing middle layer in the trilayer process is stripped atthe same time as the substrate processing. When the substrate is etchedwith a chlorine or bromine-base gas, the silicon-containing middle layermust be subsequently stripped by dry etching with a fluorocarbon-basegas after the substrate processing.

The resist bottom layer formed by the inventive method is characterizedby resistance to etching of the processable substrate. The processablesubstrate may be a substrate having a processable layer depositedthereon. The substrate includes those of Si, α-Si, p-Si, SiO₂, SiN,SiON, W, TiN, Al and the like, and a suitable material different fromthe processable layer is selected among them. The processable layer isselected from low-k films of Si, SiO₂, SiON, SiN, p-Si, α-Si, W. W-Si,Al, Cu, Al—Si, and the like and stop films thereof, and typically has athickness of 50 to 10,000 nm, especially 100 to 5,000 nm.

Referring to FIG. 1, the trilayer resist working process is described. Aresist bottom layer 3 is formed on a processable layer 2 lying on asubstrate 1, a resist middle layer 4 is formed on the bottom layer 3,and a resist top layer 5 is formed thereon (FIG. 1A). Then apredetermined region 6 of the resist top layer is exposed to radiation(FIG. 1B), PEB, and developed, forming a resist pattern 5 a (FIG. 1C).The resist middle layer 4 is etched with CF gas through the resistpattern 5 a as mask, forming a resist middle layer pattern 4 a (FIG.1D). The resist pattern 5 a is removed, and the resist bottom layer 3 isetched with oxygen plasma through the resist middle layer pattern 4 a asmask, forming a resist bottom layer pattern 3 a (FIG. 1E). The resistmiddle layer pattern 4 a is removed, and the processable layer 2 isetched through the resist bottom layer pattern 3 a as mask, forming apattern 2 a on the substrate 1 (FIG. 1F).

In the embodiment using an inorganic hard mask middle layer, the resistmiddle layer 4 is the inorganic hard mask middle layer. In the otherembodiment using BARC, a BARC layer intervenes between the resist middlelayer 4 and the resist top layer 5. Etching of BARC may be continuouslyfollowed by etching of the resist middle layer 4. Alternatively, etchingof BARC alone is performed, and after the etching system is exchanged,etching of the resist middle layer 4 is performed.

EXAMPLE

Synthesis Examples and Examples are given below together withComparative Examples for further illustrating the invention although theinvention is not limited thereby.

The weight average molecular weight (Mw) and number average molecularweight (Mn) of a polymer are determined by gel permeation chromatography(GPC) versus polystyrene standards, and a dispersity (Mw/Mn) is computedtherefrom.

Synthesis Example 1 Synthesis of Naphthalene Derivative (I)

(1-1)

A three-neck flask was charged with 15.9 g (5.6 mmol) of1,1′-bi-2,2′-naphthol, 10.0 g (5.6 mmol) of 9-fluorenone, and 125 ml of1,2-dichloroethane, which were dissolved by keeping the flask in an oilbath. After dissolution was confirmed, 0.3 ml of 3-mercaptopropionicacid and 3.0 ml of methanesulfonic acid were added dropwise. Underreflux, reaction was effected for 10 hours. At the end of reaction, thereaction solution was diluted with 300 ml of ethyl acetate, andtransferred to a separatory funnel where it was washed with water andseparated. Water washing was repeated until the water layer becameneutral. The organic layer was concentrated under reduced pressure, and100 ml of tetrahydrofuran (THF) was added to the residue, which waspoured to 1,300 ml of hexane, allowing the polymer to crystallize. Thecrystallized polymer was collected by filtration and dried in vacuum,obtaining naphthalene derivative (I).

Naphthalene Derivative (I):

Mw=3,013

Mw/Mn=1.57

IR (KBr) σmax=3529, 3060, 2969, 1912, 1620, 1596, 1500, 1474, 1447,1388, 1343, 1276, 1217, 1147 cm⁻¹

n=˜6.08 (computed from Mw), ˜4.87 (computed from ¹H-NMR)

TG-DTA (air, 30→500° C.): −23.02%

TG-DTA (He, 30→500° C.): −19.94%

Synthesis Example 2 Synthesis of Naphthalene Derivative (II)

In the formulae, x and y each indicate a proportion of the correspondingpartial structure.(1-2)

A three-neck flask was charged with 7.9 g (2.8 mmol) of1,1′-bi-2,2′-naphthol, 7.5 g (2.8 mmol) of 2,2′-dinaphthyl ether, 10.0 g(5.6 mmol) of 9-fluorenone, and 60 ml of 1,2-dichioroethane, which weredissolved by keeping the flask in an oil bath. After dissolution wasconfirmed, 0.3 ml of 3-mercaptopropionic acid and 3.0 ml ofmethanesulfonic acid were added dropwise. Under reflux, reaction waseffected for 11 hours. At the end of reaction, the reaction solution wasdiluted with 100 ml of methyl isobutyl ketone and 100 ml of toluene, andtransferred to a separatory funnel where it was washed with water andseparated. Water washing was repeated until the water layer becameneutral. The organic layer was concentrated under reduced pressure, and140 ml of THF was added to the residue, which was poured to 1,500 ml ofhexane, allowing the polymer to crystallize. The crystallized polymerwas collected by filtration and dried in vacuum, obtaining naphthalenederivative (II).

Naphthalene Derivative (II):

Mw=7,384

Mw/Mn=2.89

IR (KBr) νmax=3537, 3058, 1625, 1596, 1501, 1473, 1447, 1384, 1354,1255, 1218, 1163 cm⁻¹

x=−41.2, y=˜58.8 (computed from ¹³C-NMR)

TG-DTA (air, 30→500° C.): −17.58%

TG-DTA (He, 30→500° C.): −14.01%

Synthesis Example 3 Synthesis of Naphthalene Derivative (III)

(1-3)

A three-neck flask was charged with 24.87 g (86.8 mmol) of1,1′-bi-2,2′-naphthol, 20.0 g (86.8 mmol) of 9-benzo[b]fluorenone, and120 ml of 1,2-dichioroethane, which were dissolved by keeping the flaskin an oil bath. After dissolution was confirmed, 0.60 ml of3-mercaptopropionic acid and 6.0 ml of methanesulfonic acid were addeddropwise. Under reflux, reaction was effected for 14 hours. At the endof reaction, the reaction solution was diluted with 500 ml of ethylacetate, and transferred to a separatory funnel where it was washed withwater and separated. Water washing was repeated until the water layerbecame neutral. The organic layer was concentrated under reducedpressure, and 200 ml of THF was added to the residue, which was pouredto 1,500 ml of hexane, allowing the polymer to crystallize. Thecrystallized polymer was collected by filtration and dried in vacuum,obtaining naphthalene derivative (III).

Naphthalene Derivative (III):

Mw=3,428

Mw/Mn=1.67

IR (KBr) νmax=3534, 3064, 2964, 1916, 1621, 1595, 1502, 1478, 1444,1382, 1343, 1275, 1217, 1146 cm⁻¹

n=˜6.34 (computed from Mw), ˜5.87 (computed from ¹H-NMR)

TG-DTA (air, 30→500° C.): −20.38%

TG-DTA (He, 30→500° C.): −17.41%

Comparative Synthesis Example 1 Synthesis of Polymer 7

A flask was charged with 112.63 g (250 mmol) ofbis-6,6′-(9-fluorenylidene)-2,2′-dinaphthol and 1.16 g (2.5 mmol) ofdi-μ-hydroxo-bis[(N,N,N′,N′-tetramethylethylene-diamine)copper(II)]chloride,which were dissolved in 1,250 ml of 2-methoxyethanol. In an air opensystem at room temperature, reaction was carried out for 52 hours. Thereaction was quenched with 1,000 ml of 1N hydrochloric acid aqueoussolution. The reaction solution was extracted with 3,600 ml of methylethyl ketone and 1,050 ml of toluene, washed with water and separated.Water washing/separation was repeated until the water layer becameneutral. The organic layer was concentrated in vacuum and dried invacuum, obtaining Polymer 7.

Polymer 7:

Mw=3,073

Mw/Mn=1.66

n=˜6.68 (computed from Mw)

Polymers 1 to 3 correspond to the naphthol derivatives I to III obtainedin Synthesis Examples 1 to 3, respectively, as tabulated in Table 1-1.Comparative Polymers 4 to 6 are tabulated in Table 1-3 together withPolymer 7 in Comparative Synthesis Example 1. Bottom layer materialswere prepared by dissolving a base polymer (selected from Polymers 1 to3 and comparative Polymers 4 to 7), Additive 1 or 2, crosslinker XL1,and thermal acid generator TAG1, as shown in Table 1-2, in a solvent inaccordance with the formulation shown in Table 2 and filtering through afluoroplastic filter with a pore size of 0.1 μm. The solvent contained asurfactant FC-4430 (3M-Sumitomo Co., Ltd.).

TABLE 1-1 Synthesis Mw/ Example Mw Mn Poly- mer 1

(I) Synthesis Example 1 Naphthalene derivative (I) 3,013 1.57 Poly- mer2

(II) Synthesis Example 2 Naphthalene derivative (II) 7,384 2.89 Poly-mer 3

(III) Synthesis Example 3 Naphthalene derivative (III) 3,428 1.67

TABLE 1-2 Additive 1

Additive 2

TAG1

XL1

TABLE 1-3 Mw Mw/Mn Comparative Polymer 4

 4,300 4.30 Comparative Polymer 5

 7,600 1.96 Comparative Polymer 6

13,000 4.33 Comparative Polymer 7

 3,073 1.66

TABLE 2 Refractive index Base Acid Bake at 193 nm polymer Additivegenerator Crosslinker Solvent temperature/ n k Formulation (pbw) (pbw)(pbw) (pbw) (pbw) time value value UDL-1 Polymer 1 — — — PGMEA EyL 350°C./ 130 0.44 (15) (30) (70) 60 sec UDL-2 Polymer 2 — — — PGMEA EyL 350°C./ 130 0.44 (15) (30) (70) 60 sec UDL-3 Polymer 3 — — — PGMEA EyL 350°C./ 130 0.44 (15) (30) (70) 60 sec UDL-4 Polymer 1 Additive 1 — — PGMEAEyL 350° C./ 130 0.44 (7.5) (7.5) (30) (70) 60 sec UDL-5 Polymer 2Additive 1 — — PGMEA EyL 350° C./ 130 0.44 (7.5) (7.5) (30) (70) 60 secUDL-6 Polymer 3 Additive 1 — — PGMEA EyL 350° C./ 130 0.44 (7.5) (7.5)(30) (70) 60 sec UDL-7 Polymer 1 Additive 2 — — PGMEA EyL 350° C./ 1300.44 (7.5) (7.5) (30) (70) 60 sec UDL-8 Polymer 2 Additive 2 — — PGMEAEyL 350° C./ 130 0.44 (7.5) (7.5) (30) (70) 60 sec UDL-9 Polymer 3Additive 2 — — PGMEA EyL 350° C./ 130 0.44 (7.5) (7.5) (30) (70) 60 secUDL-10 Polymer 1 Additive 1 TAG1 XL1 PGMEA EyL 230° C./ 130 0.44 (7.5)(7.5) (2) (10) (30) (70) 60 sec UDL-11 Polymer 2 Additive 1 TAG1 XL1PGMEA EyL 230° C./ 130 0.44 (7.5) (7.5) (2) (10) (30) (70) 60 sec UDL-12Polymer 3 Additive 1 TAG1 XL1 PGMEA EyL 230° C./ 130 0.44 (7.5) (7.5)(2) (10) (30) (70) 60 sec UDL-13 Polymer 1 Additive 2 TAG1 XL1 PGMEA EyL230° C./ 130 0.44 (7.5) (7.5) (2) (10) (30) (70) 60 sec UDL-14 Polymer 2Additive 2 TAG1 XL1 PGMEA EyL 230° C./ 130 0.44 (7.5) (7.5) (2) (10)(30) (70) 60 sec UDL-15 Polymer 3 Additive 2 TAG1 XL1 PGMEA EyL 230° C./130 0.44 (7.5) (7.5) (2) (10) (30) (70) 60 sec Comparative Comparative —— — PGMEA 350° C./ 1.31 0.44 UDL-16 Polymer 4 (100) 60 sec (7.5)Comparative Comparative Additive 1 — — PGMEA 350° C./ 1.31 0.44 UDL-17Polymer 4 (7.5) (100) 60 sec (7.5) Comparative Comparative Additive 2 —— PGMEA 350° C./ 1.31 0.44 UDL-18 Polymer 4 (7.5) (100) 60 sec (7.5)Comparative Comparative Additive 1 TAG1 XL1 PGMEA 230° C./ 1.31 0.44UDL-19 Polymer 4 (7.5) (2) (10) (100) 60 sec (7.5) ComparativeComparative Comparative TAG1 XL1 PGMEA 230° C./ 1.50 0.30 UDL-20 Polymer5 Polymer 4 (2) (10) (100) 60 sec (7.5) (7.5) Comparative ComparativeComparative TAG1 XL1 PGMEA 230° C./ 1.50 0.30 UDL-21 Polymer 5 Polymer 6(2) (10) (100) 60 sec (7.5) (7.5) Comparative Comparative — — — EyL 350°C./ 1.31 0.44 UDL-22 Polymer 7 (100) 60 sec (15) PGMEA: propylene glycolmonomethyl ether acetate EyL: ethyl lactate

Measurement of Refractive Index

Each of the resist bottom layer material solutions formulated in Table 2was coated onto a silicon substrate and baked at the temperature shownin Table 2 for 60 seconds to form a bottom (or undercoat) layer of 200nm thick. Using a variable angle spectroscopic ellipsometer (VASE®) ofJ. A. Woollam Co., the refractive index (n, k) at wavelength 193 nm ofthe bottom layers (UDL-1 to 15, Comparative UDL-16 to 22) wasdetermined. The results are also shown in Table 2.

Examples 1 to 18 & Comparative Examples 1 to 7 Evaluation of SolventResistance: Loss of Film Thickness by Solvent Treatment

Each of the resist bottom layer material solutions (UDL-1 to 15 andComparative UDL-16 to 22) was coated onto a silicon substrate and bakedin air at the temperature shown in Table 3 for 60 seconds to form abottom layer film. The film thickness was measured. PGMEA was dispensedon the film and kept thereon for 30 seconds, after which the substratewas spin dried and baked at 100° C. for 60 seconds for evaporating offthe PGMEA. At this point, the film thickness was measured again,determining a difference in film thickness before and after PGMEAtreatment. The results are shown in Table 3.

CF₄/CHF₃ Base Gas Etching Test

Each of the resist bottom layer material solutions (UDL-1 to 15 andComparative UDL-16 to 22) was coated onto a silicon substrate and bakedin air at the temperature shown in Table 3 for 60 seconds to form abottom layer film of 350 nm thick. These bottom layer films wereexamined by a test of etching with CF,/CHF₃ base gas using a dry etchinginstrument TE-8500P by Tokyo Electron, Ltd. A difference in thickness ofthe polymer film before and after the etching test was determined. Theresults are also shown in Table 3.

CF₄/CHF₃ base gas etching test

Chamber pressure 40.0 Pa RF power 1,000 W CHF₃ gas flow rate 10 ml/minCF₄ gas flow rate 100 ml/min He gas flow rate 200 ml/min Time 20 sec

In Table 3, a film thickness loss is reported in a relative value(percent), provided that the film thickness loss by CF₄/CHF₃ base gasetching in Comparative Example 1 is 100. A lower percent film thicknessloss indicates greater etch resistance.

O₂ Base Gas Etching Test

Each of the resist bottom layer material solutions (UDL-1 to 15 andComparative UDL-16 to 22) was coated onto a silicon substrate and bakedin air at the temperature shown in Table 3 for 60 seconds to form abottom layer film of 350 nm thick. These bottom layer films wereexamined by a test of etching with O₂ base gas using a dry etchinginstrument TE-8500P by Tokyo Electron, Ltd. A difference in thickness ofthe polymer film before and after the etching test was determined. Theresults are also shown in Table 3.

O₂ Base Gas Etching Test

Chamber pressure 40.0 Pa RF power 100 W O₂ gas flow rate 30 ml/min N₂gas flow rate 70 ml/min Time 60 sec

In Table 3, a film thickness loss is reported in a relative value(percent), provided that the film thickness loss by O₂ base gas etchingin Comparative Example 1 is 100. A lower percent film thickness lossindicates greater etch resistance.

TABLE 3 Loss of Loss of film thickness by film thickness CF₄/CHF₃ gasetching by O₂ gas etching Loss of percent loss percent loss film basedon film based on film Bake thickness thickness loss thickness losstemperature/ by solvent in Comparative in Comparative Formulation timetreatment, Å Å Example 1 = 100 Å Example 1 = 100 Example 1 UDL-1 350°C./60 sec 5 510 86% 1968 90% 2 UDL-1 400° C./60 sec 3 503 85% 1948 89% 3UDL-2 350° C./60 sec 4 525 88% 1970 90% 4 UDL-2 400° C./60 sec 2 503 85%1946 89% 5 UDL-3 350° C./60 sec 5 537 90% 1964 90% 6 UDL-3 400° C./60sec 1 501 84% 1945 89% 7 UDL-4 350° C./60 sec 9 527 89% 1971 90% 8 UDL-5350° C./60 sec 8 531 89% 1969 90% 9 UDL-6 350° C./60 sec 10 530 89% 197290% 10 UDL-7 350° C./60 sec 8 537 90% 1960 90% 11 UDL-8 350° C./60 sec 8541 91% 1958 90% 12 UDL-9 350° C./60 sec 9 538 90% 1955 90% 13 UDL-10230° C./60 sec 5 550 92% 1971 90% 14 UDL-11 230° C./60 sec 4 548 92%1973 91% 15 UDL-12 230° C./60 sec 7 547 92% 1975 91% 16 UDL-13 230°C./60 sec 3 555 93% 1977 91% 17 UDL-14 230° C./60 sec 2 551 93% 1974 91%18 UDL-15 230° C./60 sec 3 549 92% 1987 91% Comparative 1 Comparative350° C./60 sec 2 595 100% 2180 100% Example UDL-16 2 Comparative 350°C./60 sec 3 570 96% 2040 94% UDL-17 3 Comparative 350° C./60 sec 5 57597% 2050 94% UDL-18 4 Comparative 230° C./60 sec 5 590 99% 2123 97%UDL-19 5 Comparative 230° C./60 sec 2 574 96% 2151 99% UDL-20 6Comparative 230° C./60 sec 1 560 94% 2201 101% UDL-21 7 Comparative 350°C./60 sec 3 568 95% 2102 96% UDL-22

Preparation of Silicon-Containing Middle Layer-Coating Solution

A silicon-containing middle layer-coating solution was prepared bydissolving 2.0 parts by weight of a silicon-containing polymer, shownbelow, in 100 parts by weight of a solvent PGMEA containing 0.1 wt % ofsurfactant FC-4430 (3M-Sumitomo Co., Ltd.) and filtering through afluoroplastic filter having a pore size of 0.1 μm. The solution wascoated onto the bottom layer. A middle layer film resulting from thesilicon-containing middle layer-coating solution is designated SiL-1.

Silicon-Containing Polymer:

Preparation of Resist Top Layer Material and Protective Film forImmersion Lithography

A resist top layer material was prepared by dissolving a resin, acidgenerator and basic compound in a solvent containing 0.1 wt % ofsurfactant FC-4430 (3M-Sumitomo Co., Ltd.) in accordance with theformulation shown in Table 4 and filtering through a fluoroplasticfilter having a pore size of 0.1 μm. In Tables 4 and 6, this resist toplayer material is designated SL resist for ArF.

TABLE 4 Basic Resin Acid generator compound Solvent (pbw) (pbw) (pbw)(pbw) SL resist ArF single-layer PAG1 TMMEA PGMEA for ArF resist polymer(6.6) (0.8) (2,500) (100)

The ArF single-layer resist polymer, PAG1, and TMMEA in Table 4 areidentified below.

A protective film (TC-1) for immersion lithography was prepared bydissolving a resin in a solvent in accordance with the formulation shownin Table 5 and filtering through a fluoroplastic filter having a poresize of 0.1 μm.

TABLE 5 Resin Organic solvent (pbw) (pbw) TC-1 protective film polymerdiisoamyl ether (2,700) (100) 2-methyl-1-butanol (270)

The protective film polymer in Table 5 is identified below.

Pattern Etching Test Examples 19 to 33 & Comparative Examples 8 to 14

The bottom layer material (UDL-1 to 15, Comparative UDL-16 to 22) wascoated onto a silicon wafer (diameter 300 mm) having a SiO₂ film of 200nm thick deposited thereon, and baked under the conditions shown inTable 6 to form a resist bottom layer of 200 nm thick. The bake of theresist bottom layer was done in an air atmosphere.

Formation of Silicon-Containing Resist Middle Layer SiL-1

The silicon-containing resist middle layer material SiL-1 was coatedonto the resist bottom layer and baked at 200° C. for 60 seconds to forma resist middle layer of 35 nm thick.

Formation of Resist Top Layer (SL Resist for ArF) and Protective Film

The resist top layer material (SL resist for ArF in solution form) shownin Table 4 was coated on the bottom layer and baked at 105° C. for 60seconds to form a resist top layer of 100 nm thick. The protective film(TC-1) for immersion lithography was coated on the resist top layer andbaked at 90° C. for 60 seconds to form a protective film of 50 nm thick.See Table 6.

Patterning by Immersion Lithography

The resist top layer was exposed using an ArF immersion lithographyexposure tool NSR-S610C (Nikon Corporation, NA 1.30, σ 0.98/0.65, 35°dipole polarized illumination, 6% halftone phase shift mask), baked(PEB) at 100° C. for 60 seconds, and developed for 30 seconds with a2.38 wt % aqueous solution of tetramethylammonium hydroxide (TMAH),thereby forming a positive 43 nm 1:1 line-and-space pattern.

Etching Test After Patterning

The structure was dry etched using an etching instrument Telius by TokyoElectron, Ltd. First, the silicon-containing resist middle layer (SOG)was processed through the resist pattern as mask. Then the resist bottomlayer was processed through the resulting silicon-containing resistmiddle layer pattern as mask. Finally, the SiO₂ film was processedthrough the resulting resist bottom layer pattern as mask. The etchingconditions are shown below.

Transfer of resist pattern to silicon-containing resist middle layer

Chamber pressure 10.0 Pa RF power 1,500 W CF₄ gas flow rate 75 ml/min O₂gas flow rate 15 ml/min Time 15 secTransfer of silicon-containing middle layer pattern to bottom layer

Chamber pressure 2.0 Pa RF power 500 W Ar gas flow rate 75 ml/min O₂ gasflow rate 45 ml/min Time 120 secTransfer of bottom layer pattern to SiO₂ film

Chamber pressure 2.0 Pa RF power 2,200 W C₅F₁₂ gas flow rate 20 ml/minC₂F₆ gas flow rate 10 ml/min Ar gas flow rate 300 ml/min O₂ gas flowrate 60 ml/min Time 90 sec

The cross-sectional profile of the patterns was observed under electronmicroscope S-4700 (Hitachi, Ltd.). The results are shown in Table 6.

TABLE 6 Pattern Pattern Pattern Pattern Bottom profile profile profiletwist layer Pattern after after after after Bottom bake Resist/ profileetching etching etching etching layer temp./ middle after transfer totransfer to transfer to transfer to formulation time layer developmentmiddle layer bottom layer substrate substrate Example 19 UDL-1 350° C./SL resist perpendicular perpendicular perpendicular perpendicular nil 60sec for ArF/ SiL-1 20 UDL-2 350° C./ SL resist perpendicularperpendicular perpendicular perpendicular nil 60 sec for ArF/ SiL-1 21UDL-3 350° C./ SL resist perpendicular perpendicular perpendicularperpendicular nil 60 sec for ArF/ SiL-1 22 UDL-4 350° C./ SL resistperpendicular perpendicular perpendicular perpendicular nil 60 sec forArF/ SiL-1 23 UDL-5 350° C./ SL resist perpendicular perpendicularperpendicular perpendicular nil 60 sec for ArF/ SiL-1 24 UDL-6 350° C./SL resist perpendicular perpendicular perpendicular perpendicular nil 60sec for ArF/ SiL-1 25 UDL-7 350° C./ SL resist perpendicularperpendicular perpendicular perpendicular nil 60 sec for ArF/ SiL-1 26UDL-8 350° C./ SL resist perpendicular perpendicular perpendicularperpendicular nil 60 sec for ArF/ SiL-1 27 UDL-9 350° C./ SL resistperpendicular perpendicular perpendicular perpendicular nil 60 sec forArF/ SiL-1 28 UDL-10 230° C./ SL resist perpendicular perpendicularperpendicular perpendicular nil 60 sec for ArF/ SiL-1 29 UDL-11 230° C./SL resist perpendicular perpendicular perpendicular perpendicular nil 60sec for ArF/ SiL-1 30 UDL-12 230° C./ SL resist perpendicularperpendicular perpendicular perpendicular nil 60 sec for ArF/ SiL-1 31UDL-13 230° C./ SL resist perpendicular perpendicular perpendicularperpendicular nil 60 sec for ArF/ SiL-1 32 UDL-14 230° C./ SL resistperpendicular perpendicular perpendicular perpendicular nil 60 sec forArF/ SiL-1 33 UDL-15 230° C./ SL resist perpendicular perpendicularperpendicular perpendicular nil 60 sec for ArF/ SiL-1 Comparative 8Comparative 350° C./ SL resist perpendicular perpendicular perpendicularperpendicular heavy Example UDL-16 60 sec for ArF/ twists SiL-1 observed9 Comparative 350° C./ SL resist perpendicular perpendicularperpendicular perpendicular heavy UDL-17 60 sec for ArF/ twists SiL-1observed 10 Comparative 350° C./ SL resist perpendicular perpendicularperpendicular perpendicular heavy UDL-18 60 sec for ArF/ twists SiL-1observed 11 Comparative 230° C./ SL resist perpendicular perpendicularperpendicular perpendicular heavy UDL-19 60 sec for ArF/ twists SiL-1observed 12 Comparative 230° C./ SL resist perpendicular perpendicularperpendicular perpendicular heavy UDL-20 60 sec for ArF/ twists SiL-1observed 13 Comparative 230° C./ SL resist perpendicular perpendicularperpendicular tapered heavy UDL-21 60 sec for ArF/ twists SiL-1 observed14 Comparative 350° C./ SL resist perpendicular perpendicularperpendicular perpendicular some amount UDL-22 60 sec for ArF/ of twistsSiL-1 observed

Burying of Stepped Substrate Examples 34 to 36 & Comparative Examples15, 16

On a SiO₂ deposited stepped substrate in the form of a silicon substratehaving a densely packed hole pattern having a thickness of 500 nm and adiameter of 160 nm formed thereon, a bottom layer material (UDL-1, 4, 7,Comparative UDL-16, 17) was coated and baked at 350° C. for 60 secondsso as to form a bottom layer of 200 nm thick as measured from the flatsubstrate. The coated substrate was sectioned and observed under SEMwhether or not the holes were filled with the film material down to thebottom. The results are shown in Table 7.

TABLE 7 Bottom layer Bottom layer bake formulation temp./time Buryingproperty Example 34 UDL-1 350° C./60 sec holes fully filled to bottomExample 35 UDL-4 350° C./60 sec holes fully filled to bottom Example 36UDL-7 350° C./60 sec holes fully filled to bottom ComparativeComparative 350° C./60 sec some bury failures Example 15 UDL-16Comparative Comparative 350° C./60 sec holes fully filled Example 16UDL-17 to bottom

Outgas Test Examples 37 to 39 & Comparative Examples 17, 18

A bottom layer material (UDL-1, 4, 7, Comparative UDL-16, 17) was coatedon a silicon substrate and baked at 350° C. for 60 seconds to form abottom layer of 200 nm thick. When particulate emissions were observedin a hot plate oven during the 350° C. bake, the number of particleswith a size of 0.3 μm and 0.5 μm was counted using a particle counterKR-11A (Rion Co., Ltd.). The results are shown in Table 8.

TABLE 8 Bottom layer Bottom layer bake 0.3 μm 0.5 μm formulationtemp./time particles particles Example 37 UDL-1 350° C./60 sec 2 0Example 38 UDL-4 350° C./60 sec 11 2 Example 39 UDL-7 350° C./60 sec 7 1Comparative Comparative 350° C./60 sec 501 120 Example 17 UDL-16Comparative Comparative 350° C./60 sec 1,010 621 Example 18 UDL-17

It is seen from Table 2 that the resist bottom layer film formed by theinventive method has such a refractive index that the film may bepractically used as the resist bottom layer film in the trilayer processfor immersion lithography.

It is seen from Table 3 that baking at a temperature in excess of 350°C. results in a resist bottom layer which is insoluble in the solvent(Examples 1 to 12).

It is seen from Table 3 that when thermal acid generator TAG1 andcrosslinker XL1 shown in Table 1-2 are used, a resist bottom layer whichis insoluble in the solvent can be formed even by low-temperature baking(Examples 13 to 18). As is also evident from Table 3, the rates ofCF₄/CHF₃ gas etching and O₂ gas etching of the resist bottom layerformed by the inventive method are lower than Comparative Examples 1 to7 (Comparative UDL-16 to 22), indicating very high etch resistance.

It is seen from Table 6 that when the resist bottom layer formed by theinventive method was used (Examples 19 to 33), the resist profile afterdevelopment and the profile of the bottom layer after oxygen etching andafter substrate etching were improved, and the patterns were observed tobe free of twists.

As seen from Table 7, a burying failure is found in Comparative Example15. In contrast, burying property is improved by adding monomericAdditive 1 or Additive 2 to the resist bottom layer material. However,the addition of the monomer gives rise to a problem that particles areemitted during bake to contaminate the hot plate oven as seen fromComparative Examples 17, 18 in Table 8. The resist bottom layer formedfrom the resist bottom layer material comprising the naphthalenederivative as defined herein has both the advantages of step burying andparticle prevention because particulate emission is avoided even when amonomer or low molecular weight compound is added in a relatively largeamount.

While the invention has been illustrated and described in typicalembodiments, it is not intended to be limited to the details shown.Various modifications and substitutions can be made without departing inany way from the spirit of the present invention. As such, furthermodifications and equivalents of the invention herein disclosed mayoccur to persons skilled in the art using no more than routineexperimentation, and all such modifications and equivalents are believedto be within the spirit and scope of the invention as defined by thefollowing claims.

All the patent documents cited herein are incorporated herein byreference.

Japanese Patent Application No. 2010-202660 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A naphthalene derivative having the general formula (1):

wherein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, and n is such a natural number as to provide a weight averagemolecular weight of up to 100,000 as measured by GPC versus polystyrenestandards.
 2. A naphthalene derivative comprising a partial structurehaving the general formula (2):

wherein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering.
 3. A naphthalene derivative comprising a partial structure havingthe general formula (2) according to claim 2, which is obtained fromdehydrating condensation reaction of a ketone compound having thefollowing formula (3) with 1,1′-bi-2-naphthol having the followingformula (4) and a condensable compound,

wherein cyclic structures Ar1 and Art denote a benzene or naphthalenering, said condensable compound being selected from the group consistingof benzene, naphthalene, phenanthrene, anthracene, pyrene, biphenyl,phenylnaphthalene, phenylanthracene, phenylphenanthrene, phenylpyrene,binaphthyl, naphthylanthracene, naphthylphenanthrene, naphthylpyrene,bianthracene, anthracenylphenanthrene, anthracenylpyrene,biphenanthrene, phenanthrenylpyrene, bipyrene, diphenyl ether, phenylnaphthyl ether, phenyl anthracenyl ether, phenyl phenanthrenyl ether,phenyl pyrenyl ether, dinaphthyl ether, naphthyl anthracenyl ether,naphthyl phenanthrenyl ether, naphthyl pyrenyl ether, dianthracenylether, anthracenyl phenanthrenyl ether, anthracenyl pyrenyl ether,diphenanthrenyl ether, phenanthrenyl pyrenyl ether, and dipyrenyl ether,inclusive of various position isomers, a compound having the followingformula (4a):

wherein X is a single bond or a C₁-C₂₀ alkylene or aralkylene group, andm is 0 or 1, and substituted forms of the foregoing aromatic compoundsin which hydrogen is substituted by a halogen, monovalent C₁-C₂₀hydrocarbon, hydroxyl, C₁-C₂₀ alkoxy, nitro, or cyano group.
 4. A methodfor preparing a naphthalene derivative having the following generalformula (1), comprising effecting dehydrating condensation reaction of aketone compound having the following formula (3) with 1,1′-bi-2-naphtholhaving the following formula (4),

wherein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, and n is such a natural number as to provide a weight averagemolecular weight of up to 100,000 as measured by GPC versus polystyrenestandards.
 5. A method for preparing a naphthalene derivative comprisinga partial structure having the general formula (2):

wherein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, said method comprising effecting dehydrating condensation reactionof a ketone compound having the following formula (3) with1,1′-bi-2-naphthol having the following formula (4) and a condensablecompound,

wherein cyclic structures Ar1 and Ar2 denote a benzene or naphthalenering, said condensable compound being selected from the group consistingof benzene, naphthalene, phenanthrene, anthracene, pyrene, biphenyl,phenylnaphthalene, phenylanthracene, phenylphenanthrene, phenylpyrene,binaphthyl, naphthylanthracene, naphthylphenanthrene, naphthylpyrene,bianthracene, anthracenylphenanthrene, anthracenylpyrene,biphenanthrene, phenanthrenylpyrene, bipyrene, diphenyl ether, phenylnaphthyl ether, phenyl anthracenyl ether, phenyl phenanthrenyl ether,phenyl pyrenyl ether, dinaphthyl ether, naphthyl anthracenyl ether,naphthyl phenanthrenyl ether, naphthyl pyrenyl ether, dianthracenylether, anthracenyl phenanthrenyl ether, anthracenyl pyrenyl ether,diphenanthrenyl ether, phenanthrenyl pyrenyl ether, and dipyrenyl ether,inclusive of various position isomers, a compound having the followingformula (4a):

wherein X is a single bond or a C₁-C₂₀ alkylene or aralkylene group, andm is 0 or 1, and substituted forms of the foregoing aromatic compoundsin which hydrogen is substituted by a halogen, monovalent C₁-C₂₀hydrocarbon, hydroxyl, C₁-C₂₀ alkoxy, nitro, or cyano group.
 6. A resistbottom layer material comprising a naphthalene derivative as set forthin claim 1, or a polymer comprising recurring units of the naphthalenederivative.
 7. The resist bottom layer material of claim 6, furthercomprising an organic solvent.
 8. The resist bottom layer material ofclaim 6, further comprising a crosslinker and an acid generator.
 9. Amethod for forming a resist bottom layer which is included in amultilayer resist film of at least three layers used in the lithography,comprising the steps of: coating the resist bottom layer material ofclaim 6 onto a substrate, and heat treating the coating of resist bottomlayer material at a temperature of more than 100° C. to 600° C. for 10to 600 seconds for curing.
 10. The method of claim 9 wherein the step ofcoating the resist bottom layer material onto a substrate is performedby spin coating.
 11. A process for forming a pattern in a substrate bylithography, comprising at least the steps of: forming a resist bottomlayer on a substrate by the method of claim 9, forming a resist middlelayer on the resist bottom layer using a silicon-containing resistmiddle layer material, forming a resist top layer on the resist middlelayer using a resist top layer material which is a photoresistcomposition, exposing a pattern circuit region of the resist top layerto radiation, developing the resist top layer with a developer to form aresist pattern therein, etching the resist middle layer using the resistpattern as an etching mask, etching the resist bottom layer using theresulting resist middle layer pattern as an etching mask, and etchingthe substrate using the resulting resist bottom layer pattern as anetching mask.
 12. A process for forming a pattern in a substrate bylithography, comprising at least the steps of: forming a resist bottomlayer on a substrate by the method of claim 9, forming on the resistbottom layer an inorganic hard mask middle layer which is selected froma silicon oxide film, silicon nitride film, and silicon oxynitride film,forming a resist top layer on the inorganic hard mask middle layer usinga resist top layer material which is a photoresist composition, exposinga pattern circuit region of the resist top layer to radiation,developing the resist top layer with a developer to form a resistpattern therein, etching the inorganic hard mask middle layer using theresist pattern as an etching mask, etching the resist bottom layer usingthe resulting inorganic hard mask middle layer pattern as an etchingmask, and etching the substrate using the resulting resist bottom layerpattern as an etching mask.
 13. A process for forming a pattern in asubstrate by lithography, comprising at least the steps of: forming aresist bottom layer on a substrate by the method of claim 9, forming onthe resist bottom layer an inorganic hard mask middle layer which isselected from a silicon oxide film, silicon nitride film, and siliconoxynitride film, forming an organic ARC film on the inorganic hard maskmiddle layer, forming a resist top layer on the organic ARC film using aresist top layer material which is a photoresist composition, exposing apattern circuit region of the resist top layer to radiation, developingthe resist top layer with a developer to form a resist pattern therein,etching the organic ARC film and inorganic hard mask middle layer usingthe resist pattern as an etching mask, etching the resist bottom layerusing the resulting inorganic hard mask middle layer pattern as anetching mask, and etching the substrate using the resulting resistbottom layer pattern as an etching mask.
 14. The pattern forming processof claim 12 wherein the step of forming an inorganic hard mask middlelayer is performed by CVD or ALD.
 15. The pattern forming process ofclaim 12 wherein the resist top layer material is free of asilicon-containing polymer, and the step of etching the resist bottomlayer using the middle layer pattern as an etching mask uses an oxygenor hydrogen-based etchant gas.